Design and Development of Dual Channel
ECG Simulator and Peak Detector
A thesis
submitted towards the partial fulfillment of
requirements for the award of the degree of
Master of Engineering
(Electronic Instrumentation & Control)
Submitted by
Gurpinder Kaur
Roll No. 8044210
Under the Guidance of
Mr. Mandeep Singh
Assistant Professor
&
Nirbhowjap Singh
Lecturer
Department of Electrical and Instrumentation Engineering
THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY
DEEMED UNIVERSITY
PATIALA – 147004
June 2006
Declaration
I hereby declare that the report entitled “Design and Development of Dual
Channel ECG Simulator and Peak Detector” is an authentic record of my own work
carried out as requirements for the award of degree of M.E. (Electronic Instrumentation
& Control) at Thapar Institute of Engineering & Technology (Deemed University),
Patiala, under the guidance of Mr. Mandeep Singh, Assistant Professor and Mr.
Nirbhowjap Singh, Lecturer during January to June 2006.
(---------------------------)
Gurpinder Kaur
Date: ------------------
Roll No. 8044210
It is certified that the above statement made by the student is correct to the best of our
knowledge and belief.
(-------------------------------)
Mandeep Singh
Assistant Professor, EIED
(Supervisor)
TIET, Patiala
(-------------------------------)
Nirbhowjap Singh
Lecturer, EIED
(Supervisor)
TIET, Patiala
(------------------------------)
(-------------------------------)
Mrs. Manbir Kaur
Assistant Professor& Head, EIED
TIET, Patiala
Dr. T.P. Singh
Dean of Academic Affairs
TIET, Patiala
Acknowledgement
The real spirit of achieving a goal is through the way of excellence and austerous
discipline. I would have never succeeded in completing my task without the cooperation,
encouragement and help provided to me by various personalities.
With deep sense of gratitude I express my sincere thanks to my esteemed and
worthy supervisor, Mr. Mandeep Singh, Assistant Professor and Mr. Nirbhowjap Singh,
Lecturer, Department of Electrical & Instrumentation Engineering, TIET (Deemed
University) Patiala, for their valuable guidance in carrying out this work under their
effective supervision, encouragement, enlightenment and cooperation.
I shall be failing in my duties if I do not express my deep sense of gratitude
towards Mrs. Manbir Kaur, A.P. & Head of the Department of Electrical &
Instrumentation Engineering, TIET (Deemed University) Patiala, who has been a
constant source of inspiration for me throughout this work.
I am also thankful to all the staff members of the Department for their full
cooperation and help.
My greatest thanks are to all who wished me success especially my parents.
Above all I render my gratitude to the ALMIGHTY who bestowed self-confidence,
ability and strength in me to complete this work.
Abstract
For the training of Doctors as well as for design, development and testing of
automatic ECG machines, a subject with a known abnormality of heart is essentially
required. ECG Simulator is an electronic device used to simulate such subject for the
above-mentioned purpose. The significance of the ECG simulator is that the subject has
been replaced by the Data File. In this project dual channel ECG Simulator has been
designed, developed and implemented. The waveforms can be displayed on the PC
monitor as well as output through a parallel port of the PC. Subsequently these can be
displayed on digital storage oscilloscope. The simulated electric waves are presented to
electronic peak detectors. The detected peaks exactly tally with the annotated peaks in
the given ECG database; thereby authenticating its efficacy. Prerecorded ECG Signals
with known diagnostic truths were obtained from MIT-BIH ECG database. Two channel
recordings were simulated, with a novel way to segregate the combined text file to two
different analog output channels. The simulator produces realistic ECG with the
possibility of including other biological signals, e.g. blood pressures. This program can
be used as a teaching tool as well as for testing ECG monitors.
Table of Contents
Page No.
Declaration
i
Acknowledgement
ii
Abstract
iii
Table of Contents
iv-vi
List of Figures
vii
List of Abbreviations
viii
List of Tables
Chapter 1: Introduction To ECG Simulator
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
Introduction
Components of ECG Simulator
Advantages of ECG Simulator
ECG Signal basics
50/60 Noise in ECG
ECG Amplifier
Applications of ECG Simulator
Layout of theThesis
Chapter 2: ECG Signal
2.1 Introduction
2.2 The ECG Signal Overview
2.3 The Heart rate and Rhythm
2.4 The Duration of Complexes and Interval
2.4.1 Axis
2.4.2 The P Wave
2.4.3 The PR Interval
2.4.4 The duration of QRS Complex
2.4.5 QRS Amplitude
2.4.6 The duration of ST Segment
ix
1
1
1
2
3
4
5
6
6
7
7
8
10
11
11
11
12
12
12
13
2.4.7
2.4.8
2.4.9
2.4.10
The QT Interval
The duration of the T wave
The magnitude of the T wave
The TQ Interval
Chapter 3: ECG Amplifier
3.1 Electrodes and Leads
3.2 ECG Amplifier
3.3 ORCAD Simulation
3.4 Digital Storage Oscilloscoe
3.4.1 Analog to Digital Stage
3.4.2 Clock ciruit
3.4.3 Digital to Analog Scalar storage
3.4.4 Analog to Digital Conditioning stage
3.4.5 Aliasing and Detection ciruit
Chapter 4: Hardware for Dual Channel ECG Simulator
4.1 Introduction
4.2 System Requirements and Installation
4.3 Connections
4.4 ECG Data file
4.5 Simulator Hardware Overview
4.5.1 Digital to Analog Converter
4.5.1.1 General Description
4.5.1.2 Features
4.5.1.3 Specifications
4.5.1.4 Operating Ratings
4.5.1.5 Accuracy
4.5.1.6 The Operational Amplifier
4.5.1.7 Features
4.5.2 Digital Channel Oscilloscope
4.5.3 Channel Selection
4.5.4 QRS Detection
Chapter 5: ECG Simulator Software
5.1 Introduction
5.2 Parallel Port
5.2.1 Pin Function
5.2.2 Parallel Port Programming in DOS
5.3 Direct I/O - A Windows NT I/O Port Device Driver
5.3.1
Accessing I/O Ports under NT/2000/XP
5.3.2 Starting and Installing the Direct I/O Driver
5.3.3 Features of Direct I/O
13
13
14
14
15
15
17
19
20
20
21
21
21
21
22
22
24
24
25
27
29
29
30
30
31
31
31
32
32
34
36
39
39
40
40
40
46
47
47
49
Chapter 6: Simulated Results and Observations
50
Chapter 7: Conclusions and Future Scope
57
References
58
Publications From This Research Work
59
List of Figures
Figure
Page No.
Fig.1.1
Typical ECG detailing characteristic peaks and valleys.
4
Fig.2.1
The Compartments the of heart
9
Fig.2.2
Basic electrical conduction system of heart
Fig.2.3
Definition of waves, segments and intervals in the
10
normal ECG Waveform.
11
Fig.3.1
Basic lead configuration in ECG Analysis
16
Fig.3.2
Basic circuit diagram of ECG Amplifier.
18
Fig3.3
Orcad simulation of ECG amplifier.
19
Fig.4.1
Basic elements of ECG Simulator
23
Fig.4.2
Structure of ECG Simulator.
28
Fig.4.3
Circuit connections of ECG Simulator
29
Fig.4.4
Digital Signal Oscilloscope.
32
Fig 4.5
Basic circuit connection of Sample and hold circuit
35
Fig 4.6
Pin diagram of Sample and hold IC
35
Fig 4.7
Circuit connection of QRS detection stage
38
Fig 5.1
Flowchart of simulator software
40
Fig 6.1
The peaks detected in ECG signal with leads
MLII and V5
51
List of Abbreviations
• AV
Atrioventricular.
• ADC
Analog to Digital Converter
• BPP
Bidirectional Parallel Port
• CMOS
Complementary Metal Oxide
Semiconductor
• DAC
Digital to Analog Converter
• DSO
Digital Storage Oscilloscope
• DAQ
Data Acquisition
• DMA
Direct Memory Access
• DTL
Diode Transistor Logic
• ECG
Electrocardiogram
• EPP
Enhanced Parallel Port
• ISA
Industry Standard Architecture
• IOPL
Input Output Privilege Level
• I/O
Input Output
• LED
Light Emitting Diode.
• LPT
Local Printer Terminal
• MIT-BIH
Massachusetts Institute of Technology.
Beth Israel Hospital
• PC
Personal Computer
• SA
Sinoatrial
• SPP
Standard Parallel Port
• TTL
Transistor Transistor Logic
• TSS
Task State Segment
• USB
Universal Serial Bus
List of Tables
Table No.
Page No.
Table 4.1
ECG file
26
Table 6.1
Results of mitdb/100
51
Table 6.2
Results of mitdb/102
52
Table 6.3
Results of mitdb/103
52
Table 6.4
Results of mitdb/104
53
Table 6.5
Results of mitdb/105
53
Table 6.6
Results of mitdb/108
54
Table 6.7
Results of mitdb/112
54
Table 6.8
Results of mitdb/113
55
Table 6.9
Results of mitdb/116
55
Table 6.10
Results of mitdb/117
55
Table 6.11
Results of mitdb/121
56
Table 6.12
Results of mitdb/122
56
Chapter 1: Introduction to ECG Simulator
1.1 Introduction
For clinical training of doctors to interpret the ECG of a Subject with proved
diagnosis (i.e. the exact status of subject’s heart is known through the clinical truths) we
require the Subject, ECG amplifier and Monitor. The availability of such subject may
not be practically feasible in all situations. The Doctors therefore have to mainly rely on
recorded signals, which do not give the real time experience to the Doctors.
The trend these days is to build intelligent ECG machines, which automatically
detect and classify any abnormality in the ECG signal. For design, development of
testing of these automatic machines, again the presence of the subject with the proved
diagnosis is required. An ECG simulator is device, which can simulate all types of
signals recorded previously in the real time mode. This simulator can be used both for
clinical training of doctors as well as for design, development and testing of automatic
ECG machine without having real subject for this purpose. Such ECG simulator has
been designed for this project.
1.2 Components of ECG simulator
Apart from the Personal computer (PC), the system making use of ECG Simulator has
basically three components: - DAC chip (0808), Channel selection (sample and hold
circuits), QRS Detection section (using notch filter).
DAC is a device for converting a digital (usually binary) code to an analog signal
(current, voltage or electric charge). Digital-to-analog converters are the interface
between the abstract digital world and the analog real life. Simple switches, a network of
resistors, current sources or capacitors may implement this conversion.
We have used DAC0808, 8-bit monolithic digital-to-analog converter (DAC)
featuring a full scale output current settling time of 150 ns while dissipating only 33 mW
with ±5V supplies. Relative accuracies of better than ±0.19% assure 8-bit monotonicity
and linearity while zero level output current of less than 4 µA provides 8-bit zero accuracy.
Channel selection
The ECG text file has two different columns for two leads. A program written in
C/C++ segregates these two signals and using the most significant bit as channel
identifier, two separate channels of analog output were obtained. The two separate
channels are designed by using two LF398 sample and hold ICs connected at the output
of the DAC0808. It is a monolithic sample-and-hold circuit, which utilizes BI-FET
technology to obtain ultra-high dc accuracy with fast acquisition of signal and low drop
rate. Operating as a unity gain follower, dc gain accuracy is 0.002% typical and
acquisition time is as low as 6 µs to 0.01%.
QRS Detection section
The most important part of the ECG wave is the ORS complex. The QRS
complex is a waveform that correlates to the electrical flow through the bundle branches,
from which heart rate and many other parameters can be measured. For QRS Detection,
a narrow band pass filter has been designed for each channel by using 741 operational
amplifier in inverting mode. The filter is designed to have the centre frequency 17 Hz
and Quality factor of 2.83. It removes all signal frequencies except for a particular band
(i.e. to record 14-20 Hz activity in ECG recordings). The frequencies occurring on either
side of this band are not passed. The red colored LEDs at the output of filters remains off
under normal operating conditions and flashes a specific number of times indicating
which particular channel is selected and every time the occurrence of QRS complex
(highest peak of the ECG signal).
1.3 Advantages of ECG Simulator
The use of Simulator has many advantages in the simulation of ECG waveforms, like
saving of time and another one is removing the difficulties of taking real ECG
signals with invasive and non-invasive methods. The ECG simulator enables us to
analyze and study normal and abnormal ECG waveforms without actually using the
ECG machine. The various advantages of ECG simulator are described below: -
1. No risk for patients.
2. Procedures and routine events can be practiced, such as the management of nonroutine events that may be life threatening to the patient.
3. Participants learn to use the clinical devices directly on simulator without
exposing real patients to risks.
4. Students can make mistakes without the supervisor having to intervene during
the procedure.
5. The simulator session can be temporarily interrupted to highlight significant
elements of the situation and to call attention to more suited treatment to be
adopted.
6. Constructive criticism of individual and group performance under the guidance
of instructor during review of recorded therapeutic intervention.
1.4 ECG Signal Basics.
The rhythmic behavior of the heart can be monitored and used as a diagnostic
tool to detect heart abnormalities by acquiring the electrical activity on the body surface,
across the heart, known as ECG. This electrical activity originates from the electrical
activation of muscles in the heart, inherently indicating the approach of mechanical
motion.
The electric potentials generated by the heart appear throughout the body and can
be measured across its surface. Figure1.1 displays the typical ECG waveform. An ECG
signal is characterized by five peaks and valleys labeled in with the successive letters P,
Q, R, S, T and U.
Figure 1.1: Typical ECG detailing the characteristic peaks and valleys.
An ECG signal is the superposition of action potentials that occur throughout the
heart. A typical ECG signal for one heartbeat is shown in figure 1.1.An ECG is
characterized by the P wave, the QRS wave and the T wave, with each wave created by
specific heart activities. The P wave is produced by atrial depolarization, the QRS
complex primarily by ventricular depolarization and the T wave by ventricular
repolarization. Some ECG signal also contains small amplitude U wave following the T
wave; U waves are common in slow heart rates but a prominent U wave may reflect a
heart abnormality.
An ECG signal can also be broken down into three main intervals: the P-R
interval, the Q-T interval and the S-T interval. The P-R interval is mainly caused by the
depolarization of the atrium and slow conductance of the associated impulse to the
ventricle by the atrioventricular (AV) node. The Q-T interval is defined by the
depolarization and repolarization of the ventricle. The S-T interval corresponds to the
“average duration of the plateau regions of individual ventricular cells.
1.5 50/60 Noise in ECG Signal
Signal degradation by 50/60 Hz noise (depending on the country) is a problem
with ECG signals. This noise can be regarded as the result of an electromagnetic
compatibility issue-background electromagnetic field (EMF) interference from
surrounding equipment and from building power conduits corrupt the ECG signal. When
recording an ECG signal signal’s path from the patient to machine cannot be completely
shielded from this background EMF, and other measures must be considered to either
preserve or improve the ECG signal’s quality.
An alternative to shielding would be to filter the signal after it has been sampled
and digitized and before it has been displayed on the ECG unit. This solution is possible
because the ECG signal and the 50/60 noises are uncorrelated signals. When attempting
to solve the 50/60 Hz interference problems after sampling and digitization, several
solutions can be considered. For example, 50/ 60 noise could be removed from the ECG
signal through band pass filtering, or through the use of a very narrow notch filter.
However, each of these solutions has its drawbacks. Most of the information
contained in an ECG signal found below 100 Hz, and substantial indiscriminate filtering
could not be tolerated, in terms of preserving signal clarity.
In the case of notch filter, the frequency of the electric power of the ECG signal
would have to remain relatively constant in order to remain within the notch of the filter.
This problem since ECG signals generally has very small voltages, and signal power is
at a premium. Therefore, it is the sensitivity of the signal processing that calls for
adaptive filtering. Adaptive noise cancellation requires noise to be subtracted from a
received signal using an adaptive process. The desired result is minimized signal to noise
ratio. There are two main signals involved id adaptive noise cancellation: a primary
signal and a reference signal.
1.6 ECG Amplifier
An ECG signal is usually in the range of 1mV in magnitude and has frequency
components from about 0.05 – 100 Hz. To process this signal, it has to be amplified. For
the measurement of the electrocardiogram and the other bioelectric signals, the
Differential amplifier is used.
A differential amplifier can be considered as two amplifiers with separate inputs
but with a common output terminal, which delivers the sum of two amplifier output
voltages. The main features of amplifier includes High Gain (about 1,000), 0.05 -100 Hz
frequency response, High input impedance, Low output impedance.
1.7
Applications of ECG Simulator
The simulator facilitates the teaching and learning of clinical aspects that would
otherwise be difficult or potentially dangerous to teach. Simulator aims to aid in the
development of the capabilities of the individual health care workers in practical
management and group interaction, thus improving patient safety.
Teaching and Training
Technical Procedures
Heart sounds and lung sounds
Interactive physiological modeling
Reducing the need for clinical training using real patients in
socially difficult situations.
Practicum for medical students during emergency medicine
rotations
Human performance evaluation (e.g., responding to simulated critical incidents
in emergency room or operating room.
Human factors engineering and usability engineering studies for medical
equipment.
Studies in cognitive engineering.
1.8
Layout of Thesis
This thesis is divided into various parts as mentioned above. Starting with the
Introduction in Chapter 1, the Chapter 2 gives the details of ECG signal. In this chapter
the ECG signal characteristics and applications of ECG is discussed. Chapter 3 deals
with the description of ECG Amplifier. Chapter 4 describes the ECG simulator hardware
along with Channel Selection and QRS Detection. Chapter 5 presents the Software
technique used in designing an ECG simulator. Chapter 6 shows the simulated Results
and Observations of the thesis. Chapter 7 presents the Conclusion and Future scope.
Chapter 2: ECG Signal
2.1 Introduction
“ECG” (or EKG) stands for electrocardiogram; which is a measurement of the
electrical signals that control the rhythm of the heartbeat. The heart is a muscular organ
that beats in rhythm to pump the blood through the body. The signals that make the
heart’s muscle fibers contract come from the senatorial node, which is the natural
pacemaker of the heart.
The ECG is a method of recording the electrical activity of the heart. Each
heartbeat is caused by a section of the heart generating an electrical signal which then
conducts through specialized pathways to all parts of the heart. These electrical signals
also get transmitted through the chest to the skin where they can be recorded.
An ECG is performed by placing 12 recording leads at certain specific locations
on the body. They only record the heart's electrical activity. They do not produce any
electricity of their own. The test does not hurt and has no known side effects. It does not
require any preparation (except for possibly shaving chest hair to get a better recording).
The recording itself takes only a few seconds. Including the setup time and the time to
disconnect the leads, the whole procedure takes about 5 minutes.
In an ECG procedure, the electrical impulses made while the heart is beating are
recorded and usually printed out on a piece of paper. This is known as
electrocardiogram, and records any problems with the heart’s rhythm, and the
conduction of the electrical signal through the heart, which may be affected by
underlying heart disease.
An ECG can be used to assess if the patient has had a heart attack or evidence of
previous heart attack. An ECG can be used to monitor the effect of medicines used for
coronary artery disease. These are the main issues that ECG helps doctors with heart
attacks. By looking at the electrical patterns on an ECG, doctor can determine the nature
of an erratic heartbeat. There are many different types of abnormal heart beats. Not all
require treatment. In those that do, the ECG recording lets the doctor know which
treatment is best. The presence of a heart attack. It can also be determined whether the
heart attack is old or recent. The possibility that there are narrowed arteries in the heart,
which may lead to the heart attack in the future. Whether or not discomfort in the chest
is being caused by the heart. Degeneration of the conduction system of the heart which
can lead to dangerously slow heart beats.
This condition is often treated with a pacemaker. The cells that constitute the
ventricular myocardium are coupled together by gap junctions, which for the normal
healthy heart, have a very low resistance. As a consequence, activity in one cell is
readily propagated to neighboring cells. It is said the heart behaves as a syncytium; a
propagating wave once initiated continues to propagate uniformly into the region that is
still at rest.
The equivalent fibers are a valid representation because they are consistent with
the syncytial nature of the heart. In fact, because the syncytium reflects connectivity in
all directions, we may choose the fiber orientation at our convenience (so long as the
quantitative values of conductivity assigned to the fibers correspond to those that are
actually measured).
2.2 ECG Signal- An Overview
As shown in figure 2.1, heart is divided into four chambers. The upper two
chambers, left and right atria are synchronized to act together. Similarly the two lower
chambers, the ventricles, operate together. The right atrium receives the blood from the
veins of the body and pumps it into the right ventricle. The right ventricle pumps the
blood through the lungs, where it is oxygenated. The oxygen-enriched blood then enters
the left atrium, from which is pumped into the left ventricle. The left ventricle pumps the
blood into the arteries to circulate throughout the body.
The heart is a pump that pushes blood through the body. Blood enters the heart at
a low pressure and leaves at a higher pressure. It is this high arterial pressure that
provides the energy to force blood through the circulatory system. Bloods returning from
the body is sent to the right side of the heart and then to the lungs to pick up oxygen and
release carbon dioxide.
The oxygenated blood is then sent to the left side of the heart and back to the
body, where oxygen is liberated and carbon dioxide is collected. The complete left/right
division of the heart insures that there is no mixing of deoxygenated blood in the right
side) with oxygenated blood (n the left side).
Figure 2.1: The compartments of the heart.
The mammalian heart is auto rhythmic, meaning it will continue to beat if
removed from the body (and kept in an appropriate solution). Heart contractions are,
therefore, not dependent upon the brain; rather, the rhythm comes from within the heart
itself. The heart is composed almost entirely of large, strong muscle fibers, which are
responsible for the pumping action of the heart. Other cardiac muscle cells are weakly
contractile and produce the rhythm for, and conduct it to, the rest of the heart.
A group of these weak muscle cells is located in the sinoatrial (SA) node and acts
as the pacemaker for the heart. These cells rhythmically produce action potentials, which
spread via gap junctions to fibers of both right and left atria. The resulting contraction
pushes blood into the ventricles.
While adjacent atrial fibers are connected by gap junctions, the only electrical
connection between the atria and the ventricles is via the atrioventricular (AV) node. The
action potential spreads slowly through the AV node and then rapidly through the
Bundle of His and Purkinje fibers to excite both ventricles.
The semi lunar valves are located between the ventricles and the artery on each
side of the heart. In the relaxed heart, the high arterial pressure shuts the semi lunar
valves and prevents back flow from the artery into the ventricles. Ventricular contraction
increases the pressure of the blood in the ventricle (systole).
When the ventricular pressure is greater than the arterial pressure, the semi lunar
valves open and blood flows into the artery. The myocardium then relaxes (diastole), the
ventricular pressure declines, and the semi lunar valves close. The regular pattern of
peaks produced by the heart repeats for each heartbeat. This pattern of potential peaks is
called the electrocardiogram of ECG. The initial small peak, the P-wave, marks the
contraction of the atria. The larger peaks following the P-wave, the QRS complex, is a
superposition of atrial relaxation and ventricular contraction.
2.3 The Heart Rate and Rhythm
Figure 2.3 shows the compartments and electrical conduction system of the heart.
Figure 2.2: Basic conduction system of the heart.
Normally, the heart of an adult is depolarized 60 to 90 times per minute. A
depolarization rate lower than this is called sinus bradycardia, while one that is higher is
called sinus tachycardia. The heart rate of the normal newborn is much higher than that
of an adult. The heart rate can be calculated by dividing the R-R interval into 60. This
number is denoted BPM (Beats per minute).
Figure 2.3: Definition of waves, segments and intervals in the normal ECG
waveform.
2.4 The Duration of the Complexes and Interval
After determining the heart rate and rhythm, the clinician should measure the
duration of the waves and intervals on the electrocardiogram.
2.4.1 Axis
The axis is the general direction of the electrical impulse through the heart. It is
usually directed to the bottom left (normal axis: -30o to +90o), although it can deviate to
the right in very tall people and to the left in obesity.
•
Extreme deviation is abnormal and indicates a bundle branch block, ventricular
hypertrophy or (if to the right) pulmonary embolism.
•
It also can diagnose dextrocardia or a reversal of the direction in which the heart
faces, but this condition is very rare and often has already been diagnosed by
something else (such as a chest X-ray).
2.4.2 The P wave
The duration of P wave is measured from the beginning of the P wave to the end.
In normal adults, this period is usually less than 0.12 seconds; in neonates, it is less than
0.08 second. This is the time interval required for the wave of depolarization to spread
through the atria and to reach the atrioventricular node. The amplitude of P waves of the
normal adult is less than 0.25mV in the extremity leads and smaller than this in children.
2.4.3 The PR Interval
The PR interval represents the amount of time required for the depolarization
process to spread from its origin in the sinus node, through the atria, to and through the
atrioventricular node (where the impulses are delayed), down the bundle branches and
their sub branches (including the purkinje fibers), and to the ventricular muscle. It is
measured from the beginning of the P wave to the beginning of the QRS complex.
In reality, this interval should be called the PQ interval, but convention holds that
it is called the PR interval. When there is no Q wave, the measurement is made from the
beginning of the P wave to the beginning of the R wave.
The difference between the intervals as measured to the beginning of the Q wave,
and as measured to the R wave, is usually about 0.02 second but may be as much as 0.04
second. The PR interval is less than 0.20 second in the normal adult and much less than
this in normal children.
2.4.4 The Duration of the QRS Complex
The duration of the QRS complex represents the amount of time required for the
depolarization of the ventricular musculature. It is measured from the beginning of the Q
wave to the end of the S wave. In normal adults, the QRS duration is usually 0.10 second
or less and in children, it is usually less than 0.08 second. When the QRS duration is
greater than 0.10 second in adults, it is proper to consider the presence of some type of
ventricular conduction defect.
2.4.5 QRS Amplitude
The normal QRS voltage may be as small as 0.5 - 0.7mV, but it is usually greater
than this. IT is generally accepted that the QRS voltage is definitely small, when it
measures 0.4 mV or less in all the extremity leads. When this occurs, it is wise to
consider certain abnormalities as possible causes.
2.4.6 The Duration of the ST Segment
The duration of the ST segment represents the amount of time during which the
ventricular musculature is depolarized. The depolarization process ends with the end of
the QRS complex, and the repolarization begins with, or before, the beginning of the T
wave. In some patients, the repolarization process begins during the ST segment.
The ST segment duration is determined by measuring the interval of time from
the end of the S wave to the beginning of the T wave. In practice, a prolonged ST
segment is identified by detecting a prolonged QT interval, while the duration of the T
wave remains normal.
2.4.7 The QT Interval
The QT interval represents the amount of time required for depolarization of the
ventricles, plus the amount of the during which the ventricles are excited (ST segment),
plus the amount of the time required for their repolarization (T wave). This interval
represents the duration of electrical systole, which is different from the duration of
mechanical systole.
The QT interval is measured from the beginning of the Q wave of the QRS
complex to the end of the T wave. The duration of the QT interval varies with age,
gender, and heart rate. It should not exceed 0.40 second, when the heart rate of an adult
is 70 depolarization per minute.
2.4.8
The Duration of the T Wave
The T wave is produced by the repolarization process. The duration of the T
wave is measured from the beginning of the wave to the end. The repolarization process
undoubtedly begins before the T wave and is sometimes quite visible as a displaced ST
segment, which is referred to as “early repolarization.” Although the duration of the
normal T wave has been studied, and tables have been constructed using the data, the
actual measurement is rarely performed in practice.
2.4.9 The Magnitude of the T wave
The area encompassed by the T wave may be a little smaller or a little larger than
that encompassed by the QRS complex; it is usually about two-thirds that of the latter.
Characteristically, the upstroke of the normal T wave is less steep than the down stroke.
2.4.10 The TQ Interval
The TQ Interval is measured from the end of the T wave to the beginning of the
next Q wave. During this period the ventricles are polarized and waiting for stimulation
that initiates depolarization. Under the pathological conditions, several changes may
occur in the ECG. These include: 1.
Altered paths of excitation in the heart.
2.
Changed Origin of waves.
3.
Altered relationships of features.
4.
Changed magnitudes of one or more features.
5.
Differing durations of waves or intervals.
The instrument used to obtain and record the electrocardiogram is called an
electrocardiograph.
Chapter 3: ECG Amplifier
For the measurement of the electrocardiogram and the other bioelectric signals,
the Differential amplifier is used. A differential amplifier can be considered as two
amplifiers with separate inputs but with a common output terminal, which delivers the
sum of two amplifier output voltages.
3.1 Electrodes and Leads
To record the ECG, a number of electrodes are affixed to the body of the patient.
The electrodes are connected to the ECG machine by the same number of electrical
wires. Current flow, in the form of ions, signals contraction of cardiac muscle fibres
leading to the heart's pumping action. The ECG is a valuable, non-invasive diagnostic
tool which was first put to clinical use in 1913 with Einthoven's invention of the string
galvanometer. Einthoven's recording is known as the "three lead" ECG, with
measurements taken from three points on the body (defining the "Einthoven triangle" —
an equilateral triangle with the heart at the centre.) The difference between potential
readings from L1 and L2 is what is used to produce the output ECG trace. The L3
connection establishes a common ground for the body and the recording device
(oscilloscope.)
The voltage generated by the pumping action of the heart is actually a vector
whose magnitude, as well as spatial orientation, changes with time. The ECG waveform
is dependent on the placement of the electrodes. Usually 5 electrodes are affixed to the
body of the patient. The placement of electrodes, as well as the color code is used to
identify the each electrode. In the normal electrode placement, 4 electrodes are used to
record the ECG.
The right leg is used only for the ground reference and the left leg is selected
because it terminates vertically below the heart. The three bipolar limb lead selections
first introduced by Einthoven are as follows:
Lead 1
-
Left arm (LA) and Right arm (RA).
Lead 2
-
Left leg (LL) and Right arm (RA).
Lead 3
-
Left leg (LL) and Left arm (LA).
Figure 3.1 Basic Lead Configuration in ECG analysis
These three leads are called bipolar because for each lead the ECG is recorded from two
electrodes and the third electrode is not connected. The 12 standard leads used most
frequently are displayed in figure 3.1.
The Einthoven postulated that at any given instant of cardiac cycle, the frontal
plane representation of electrical axis of heart is two-dimensional vector. And the ECG
measured from any one of the three basic limb lead is a time-variant single dimensional
component of that vector.
Einthoven also made the assumption that the heart is near to the center of the
equilateral triangle, the apexes of which are the right and left shoulder and the crotch. By
assuming that the ECG potentials at the shoulders are essentially the same as the wrists
and that the potentials at the crotch differ little from those at either ankle, he let the
points of this triangle represent the electrode positions for the three limb leads. This
triangle called the Einthoven triangle is shown.
The instantaneous voltage measured from any one of the three limb lead
positions is approximately equal to the algebraic sum of the other two, or that the vector
sum of the projections on all three lines is equal to zero. In unipolar limb leads, one of
the limb electrodes is used as an exploratory electrode as well as contributing to the
central terminal.
3.2 ECG Amplifier
An ECG signal is usually in the range of 1mV in magnitude and has frequency
components from about 0.05 – 100 Hz. To process this signal, it has to be amplified. The
above figure shows the circuit of ECG amplifier. The typical characteristics of an ECG
amplifier are: 1.
High Gain (about 1,000)
2.
0.05 -100 Hz Frequency response.
3.
High input impedance.
4.
Low output impedance.
Monitoring systems typically use the bandwidth of 0.5 – 50 Hz. Various filters
like High pass, low pass, band pass , band stop are used to build an ECG amplifier. The
inputs RA and LA are given to separate low pass filters. The low pass filters have the
low – frequency gain,
AL = -R2/ R1
The negative sign results because the op amp is in an inverting amplifier
configuration. The high corner frequency is given by: Fh = 1/ 2 * ∏ * R2* C1
A low pass filter acts as an integrator at high frequencies. The integrator output
is given by: V0 = - Vi / 1 +j*w*R1*C1
= - ∫ (VI) / R1*C1
Figure 3.2 Basic circuit diagram of ECG amplifier
The basic diagram of ECG amplifier is shown in figure 3.2. This circuit amplifies
the differential ECG signals & introduces a small level shift to bring the negative signals to the
positive side and feeds the input of ADC. This circuit has differential Amplifier followed by a
High Pass Filter, a non-inverting amplifier with a variable gain and finally a level shifter that
adds a 1V offset to the amplified ECG signal.
The high pass filter act like a differentiator at low frequencies. The differentiator
gain increases with frequency, up to the low corner frequency. The basic diagram of
ECG amplifier is shown
3.3 ORCAD Simulation
Figure 3.3 shows the ECG Amplifier that is simulated using Orcad 9.2 lite
edition.
7
V+
Vvcc
vee
4
5Vdc7
5v
vcc
R35
U5
3
> +
OS2
OUT
1k
2
C2
uA741
1n
V1
0
5Vac
0Vdc
OS1
vee
5
R23
0
R22
0
V+
6
1k
1
R34
7
vcc
1kV+
U6
3
+
OS2
V-
OUT
2
R33
4
1k
R25
+
1k
1n
0
0
2
uA741
4
1
C6
1n
OS2
OUT
C3
OS1
V-
6
vcc
U8
3
uA741
5
5
R32
6
1k
7
R8 10k
1
OS1
vee
V+
R28
1k
V-
vee
R30
0
4
1k
vcc
U7
3
+
R31
OS2
OUT
1k
2
> uA741
0
OS
5
6
1
R29 vee
R26
>
R27
1k
1k
1k
0
C5
Title
<Title>
Size
A
Date:
Document Number
<Doc>
Rev
<RevCode>
Tuesday, November 08, 2005 Sheet
1
of
1
Figure 3.3 ORCAD Simulation of ECG Amplifier
1n
3.4 Digital storage Oscilloscope
To display analog signal onto a digital computer, such as PC, the continuous
analog voltage needs to be converted into a discrete digital number that the computer can
then take and manipulate.
3.4.1 Analog to Digital Stage
The conversion between analog to digital is done using an A/D converter chip.
The continuous signal is changed into discrete signal this implies the faster of an A/D
converter we have, the better we will represent the continuous analog signal into discrete
digital as well as the fact that we will be able to accurately reproduce higher frequency
waves. Today, two methods in A/D technologies seem to give the best speed
performance. One is sequential approximation, in which the analog voltage is
approximated by sequentially moving from the most significant bit to least significant bit
and comparing the digital voltage to the analog voltage. The method works similarly to a
binary search in which we do a binary search for the digital number that best represents
the analog voltage.
One drawback to this method is the fact that the chip must also contain a digital
to analog stage to transform the digital voltage into analog and compare it with the
analog input. The second, and by far the most popular method for use in high speed
electronics, is a flash A/D converter. Suppose that one uses an 8 bit converter. Then, 256
(2^8) comparators are stacked one on top of each other and the input voltage is passed
through a 256 resistor network ladder. The resistor network will distribute the input
voltage evenly on each resistor and the comparators compare each node signal against a
fixed reference voltage. Based on how many comparators are "on" at one time, a digital
number representing the input voltage can be obtained.
In my design, I have used Motorola's triple 8-Bit Video ADC (MC44250).This flash
A/D converter has the following feature which made it extremely well suited for my
project:15MHz Sampling Rate.
Single 5Volt Power Supply.
Flash A/D converters on one chip. (Very well suited for future upgrades where we
would like our digital scope to have two or three input channels).
Depending on the environment in which the circuit is being built, large coupling
capacitors might be necessary in order to remove any excessive noise around the
components (one environment in which this applies is when the circuit is built using a
breadboard).
3.4.2 Clock Circuit
The A/D converter requires a clock running at speeds up to 15MHz.Again,
caution should be taken on where and how the clock is mounted in the circuit. On a
breadboard, the high clock frequencies will cause excessive noise causing certain
components to malfunction.
3.4.3 Digital to Analog Scalar Stage
However the D/A converter is rated for only 25V. By using the 3K and 1K
resistors it can be made sure that we have a 25V input to the DAC when the original
wave is 100V. The rest of the circuit acts just like an inverting amplifier where we are
using the DAC as the feedback voltage. Using this setup we are able to divide the input
signal by a factor ranging from 4 to 1024.
3.4.4 Analog to Digital Conditioning Stage
The A/D converter requires the input voltage for Vin to range from around 1.7
volts to about 4.9 volts, with an average range of about 3 volts. Moreover, since the
A/D data specs did not contain any information on the input impedance it would be
nice to have something that would provide high impedance to the analog input as well
as shift the voltage in the +2V to +5V range.
3.4.5 Aliasing Detection Circuit
When sampling continuous signals caution should be taken to prevent aliasing.
By definition alias is a false signal caused from beats between signal frequency and
sampling frequency. In 1928 Nyquist discovered that in order to prevent aliasing the
signal must be sampled at a frequency twice its own. That’s why it is appropriate to
incorporate an alias detection circuit in PC Oscilloscope.
Chapter 4: Hardware for Dual Channel ECG
Simulator
4.1 Introduction
Electrocardiogram is record of electrical activity of human heart and is of vital
utility to know the status of heart. Each heartbeat is caused by a section of the heart
generating an electrical signal that then conducts through specialized pathways to all
parts of the heart. These electrical signals also get transmitted through the chest to the
skin where they can be recorded.
For clinical training of doctors to interpret the ECG of a Subject with proved
diagnosis (i.e. the exact status of subject’s heart is known through the clinical truths) we
require the Subject, ECG amplifier and Monitor. The availability of such subject may
not be practically feasible in all situations. The Doctors therefore have to mainly rely on
recorded signals that do not give the real time experience to the Doctors.
The trend these days is to build intelligent ECG machines which automatically
detect and classify any abnormality in the ECG signal. For design, development of
testing of these automatic machines, again the presence of the subject with the proved
diagnosis is required.
The figure 4.1 shows the various segments of the ECG simulator. The text file of
ECG signal with proper annotation (Markings) is downloaded from Physionet.org and
stored in the folder. By using ‘C’ program, this file is compiled and its executable file
i.e. ECG.EXE is stored in the same folder. Upon running this executable file, the signal
from the parallel port of PC is transferred to DAC0808. The ECG text file has two
different columns for two leads. A program written in C/C++ segregates these two
signals and using the most significant bit as channel identifier, two separate channels of
analog output are obtained.
Figure 4.1 Basic Elements of ECG Simulator
The channel is selected by feeding the MSBs of the signal to the selection logic
input of the sample and hold ICs. The narrow band pass filter is designed by using 741
operational amplifier, to detect the QRS complex from the ECG signal. The red colored
LEDs at the output of filters remains off under normal operating conditions and flashes a
specific number of times indicating which particular channel is selected and every time
the occurrence of QRS complex (highest peak of the ECG signal).
An ECG simulator is device that can simulate all types of signals recorded
previously in the real time mode. This simulator can be used both for clinical training of
doctors as well as for design, development and testing of automatic ECG machine
without having real subject for this purpose. Such ECG simulator has been designed for
this project.
4.2 System Requirements and Installation
For the proper working of ECG Simulator, system must meet the following
minimum requirements
•
Personal computer using a 233 MHz Pentium-class processor. Using a Pentium
III or Celeron 600 MHz or equivalent is recommended.
•
Compiler installed on PC for execution of the application program.
•
Microsoft Windows 2000/NT/XP.
•
Direct I/O device driver for accessing the parallel port of Windows XP
(whichever is used).
.
•
Source code written in any language like C / C++, visual basics etc
•
ECG Data file of patient loaded from site www.physionet.org
•
Complete hardware for displaying ECG wave, Channel selection, QRS detection
circuitry.
4.3 Connections
A Program is written in C language, which reads the data of ECG file and sends
it to the port of the PC.
Direct I/O device driver is installed, which allows us to access parallel port
Parallel port of the PC is used to send data to the DAC chip. 8 pins of the parallel
port are used for transferring the data (2 to 9) and rests are grounded.
DAC is provided with power supply and other reference voltages.
A 741 operational amplifier is connected to the output of the DAC for converting
the output current into output voltage.
The main circuit for Channel Selection comprising of LF398 ICs and QRS
Detection by using notch filters are connected to DAC.
We can have monitor or DSO for taking display of real time ECG Signal and it is
directly connected to power supply.
LEDs connected glow according to ECG signal which represents the selection of
channel and detection of QRS complex.
4.4 ECG Data file
The ECG data file is taken from the ECG Databases available at site
www.physionet.org. Several databases of ECG and other physiological recordings are
available for various purposes including the evaluation of ECG analyzers. Of particular
relevance is PhysioNet, apparently the largest and best-organized network at present.
The project offers free access via the web to large collections of recorded physiologic
signals and related open-source software. There are many databases available in the
PhysioBank archives, organized according to the types of signals and annotations
contained in each database. For e.g. –
•
Multi-Parameter Databases. Available signals vary, but may include
ECG, continuous invasive blood pressure, respiration, oxygen saturation,
and EEG, among others.
•
ECG Databases
•
MIT-BIH ECG Compression Test Database
•
Interbeat (RR) Interval Databases. These contain beat annotations
obtained from ECG recordings, but the ECG signals are not available.
•
Neurological Databases
•
Synthetic databases
•
Gait Dynamics in Neuro-Degenerative Disease Database
The data file is the record (of a heart patient) obtained from mit.bh database
(Massachusetts Institute of Technology. Beth Israel Hospital.). This is a rich database
containing hundreds of recordings extending over 200 hours. The recordings were
digitized at 360 samples per second per channel with 11-bit resolution over a 10 mV
range. Approximately all of the signals have been annotated on beat-by-beat basis.
During 1989 CD ROM was produced containing the original MIT-Arrhythmia along
with many assembled recordings for various research projects between 1981 and 1989.
There are approximately 600 M bytes of digitized ECG recordings, mostly with beat-bybeat annotations [Moody and Mark, 1990]. This data was made available on Internet
during September 1991,on physionet (http:/www.physionet.org). It is a web-based
resource that supplies physiologic signals and the related open source software to biomedical field. The MIT-BIH Arrhythmia Database contains 48 half-hour excerpts of
two-channel ambulatory ECG recordings, obtained from 47 subjects studied by the BIH
Arrhythmia Laboratory between 1975 and 1979. The recordings were digitized at 360
samples per second per channel with 11-bit resolution over a 10 mV range. Two or more
cardiologists independently annotated each record; disagreements were resolved to
obtain the computer-readable reference annotations for each beat (approximately
110,000 annotations in all) included with the database. This directory have the complete
MIT-BIT Arrhythmia-database. Almost half i.e. 25 out of 48 complete records, and
reference annotation files for all 48 records has been freely available here since
physionet’s inception in September 1999[Goldberger et al.2000].
Table 4.1 ECG Data file
TIME
CHANNEL 1
CHANNEL 2
In volts
In volts
0.361
-0.335
-0.205
0.364
-0.335
-0.190
In seconds
0.367
-0.340
-0.180
0.369
-0.330
-0.185
0.372
-0.340
-0.200
0.375
-0.350
-0.215
0.378
-0.355
-0.205
0.381
-0.350
-0.210
0.383
-0.345
-0.200
0.386
-0.330
-0.185
0.389
-0.320
-0.205
0.392
-0.335
-0.200
0.394
-0.330
-0.210
0.397
-0.345
-0.205
0.400
-0.330
-0.185
0.403
-0.335
-0.185
0.406
-0.335
-0.200
0.408
-0.345
-0.215
0.411
-0.345
-0.225
0.414
-0.355
-0.220
0.417
-0.340
-0.200
0.419
-0.340
-0.200
0.422
-0.335
-0.215
0.425
-0.330
-0.225
4.5 Simulator Hardware Overview
The below figure shows basic structure of the ECG simulator. By using ‘C’
program, this file is compiled and its executable file i.e. ECG.EXE was stored in the
same folder. Upon running this executable file, the signal from the parallel port of PC is
transferred to DAC0808. The significance of the ECG simulator is that the subject has
been replaced by text file
The ECG text file has two different columns for two leads. A program written in
C/C++ segregates these two signals and using the most significant bit as channel
identifier, two separate channels of analog output were obtained.
The two separate channels are designed by using two LF398 sample and hold ICs
connected at the output of the DAC0808. The ECG wave can be displayed on the PC
monitor as well as at the Digital storage oscilloscope connected at the output of DAC.
Figure 4.2 Structure of ECG Simulator
Figure 4.3 Circuit connections of ECG Simulator
The digital output of the parallel port is connected to DAC 0808(Digital-toAnalog Converter). DAC 0808 is an 8 bit digital to analog converter. The digital output
signal is converted to analog signal by the DAC. The reference voltage given to pin 14
decides the output range. The DAC output is current in the milli amperes range. This
current is converted into voltage by 741 opamp as shown in figure 4.3. The feedback
resistance RF connected between the pins 2 and 6 decides the conversion ratio. The
output of the opamp is in the range of few volts.
4.5.1 DIGITAL TO ANALOG CONVERTER (DAC 0808)
4.5.1.1 General Description: - The DAC0808 is an 8-bit monolithic digital-to-analog
converter (DAC) featuring a full scale output current settling time of 150 ns while
dissipating only 33 mW with ±5V supplies. Relative accuracies of better than ±0.19%
assure 8-bit monotonicity and linearity while zero level output current of less than 4 µA
provides 8-bit zero ac-curacy
The power supply current of the DAC0808 is independent of bit codes, and
exhibits essentially constant device characteristics over the entire supply voltage range.
The DAC0808 will interface directly with popular TTL, DTL or CMOS logic levels, and
is a direct replacement for the MC1508/MC1408. For higher speed applications,
DAC0800 data sheet can be viewed.
4.5.1.2 Features:•
Relative accuracy: ±0.19% error maximum.
•
Full scale current match: ±1 LSB typ.
•
Fast settling time: 150 ns type.
•
Non inverting digital inputs are TTL and CMOS compatible.
•
High speed multiplying input slew rate: 8 mA/µs.
•
Power supply voltage range: ±4.5V to ±18V.
•
Low power consumption: 33 mW @ ±5V.
4.5.1.3 Specifications
Power Supply Voltage
•
VCC
+18 VDC
•
VEE
- 18 VDC
•
Digital input voltage, v5-v12
- 10 VDC to + 18 VDC
•
Applied Output Voltage, V0
-11 VDC to + 18 VDC
•
Reference Current, I14
5mA
•
Reference Amplifier Inputs,
VCC,VEE ,V14, V15
•
Power Dissipation
1000 m W
•
ESD Susceptibility
TBD
•
Dual-In-Line Package (Plastic)
260°C
• Dual-In-Line Package (Ceramic)
300°C
4.5.1.4 Operating Ratings
Temperature Range
DAC0808
TMIN< TA < TMAX
0 < TA < + 75°C
4.5.1.5 Accuracy
Absolute accuracy is the measure of each output current level with respect to its
intended value, and is dependent upon relative accuracy and full-scale current drift.
Relative accuracy is the measure of each output current level as a fraction of the fullscale current. The relative accuracy of the DAC0808 is essentially constant with
temperature due to the excellent temperature tracking of the monolithic resistor ladder.
The reference current may drift with temperature, causing a change in the absolute
accuracy of output current. However, the DAC0808 has a very low full-scale current
drift with temperature.
Two 8-bit D-to-A converters may not be used to construct a 16-bit accuracy Dto-A converter. 16-bit accuracy implies a total error of ± 1 .2 of one part in 65,536 or
±0.00076%, which is much more accurate than the ±0.019% specification provided by
the DAC0808.
4.5.1.6 Operational amplifier
The mA741 is a high performance operational amplifier with high open-loop
gain, internal compensation, high common mode range and exceptional temperature
stability. The mA741 is short-circuit-protected and allows for nulling of offset voltage.
The DAC output is current in the milli amperes range. This current is converted
into voltage by 741 opamp. The feedback resistance RF connected between the pins 2
and 6 decides the conversion ratio. The output of the opamp is in the range of few volts.
4.5.1.7 Features
• Internal frequency compensation.
• Short circuit protection.
• Excellent temperature stability.
• High input voltage range.
4.5.2 DIGITAL STORAGE OSCILLOSCOPE
The output of the simulator can be connected to a digital storage oscilloscope to get
a clear picture of the waveform. For further analysis, the output can also be fed to a
computer through the soundcard.
Figure 4.4 Digital storage oscilloscope
The conversion between analog to digital is done using an A/D converter chip.
The continuous signal is changed into discrete signal this implies the faster of an A/D
converter we have, the better we will represent the continuous analog signal into discrete
digital as well as the fact that we will be able to accurately reproduce higher frequency
waves. Today, two methods in A/D technologies seem to give the best speed
performance.
One is sequential approximation, in which the analog voltage is approximated by
sequentially moving from the most significant bit to least significant bit and comparing
the digital voltage to the analog voltage. The method works similarly to a binary search
in which we do a binary search for the digital number that best represents the analog
voltage. One drawback to this method is the fact that the chip must also contain a digital
to analog stage to transform the digital voltage into analog and compare it with the
analog input.
The second, and by far the most popular method for use in high speed electronics, is a
flash A/D converter. Suppose that one uses an 8 bit converter. Then, 256 (2^8)
comparators are stacked one on top of each other and the input voltage is passed through
a 256-resistor network ladder. The resistor network will distribute the input voltage
evenly on each resistor and the comparators compare each node signal against a fixed
reference voltage. Based on how many comparators are "on" at one time, a digital
number representing the input voltage can be obtained .In my design; I have used
Motorola's triple 8-Bit Video ADC (MC44250).
Depending on the environment in which the circuit is being built, large coupling
capacitors might be necessary in order to remove any excessive noise around the
components (one environment in which this applies is when the circuit is built using a
breadboard). The A/D converter requires a clock running at speeds up to 15MHz.Again,
caution should be taken on where and how the clock is mounted in the circuit. On a
breadboard, the high clock frequencies will cause excessive noise causing certain
components to malfunction.
However the D/A converter is rated for only 25V. By using the 3K and 1K
resistors it can be made sure that we have a 25V input to the DAC when the original
wave is 100V. The rest of the circuit acts just like an inverting amplifier where we are
using the DAC as the feedback voltage. Using this setup we are able to divide the input
signal by a factor ranging from 4 to 1024.
The A/D converter requires the input voltage for Vin to range from around 1.7
volts to about 4.9 volts, with an average range of about 3 volts. Moreover, since the A/D
data specs did not contain any information on the input impedance it would be nice to
have something that would provide high impedance to the analog input as well as shift
the voltage in the +2V to +5V range.
When sampling continuous signals caution should be taken to prevent aliasing.
By definition alias is a false signal caused from beats between signal frequency and
sampling frequency. In 1928 Nyquist discovered that in order to prevent aliasing the
signal must be sampled at a frequency twice its own. That’s why it is appropriate to
incorporate an alias detection circuit in PC Oscilloscope
4.5.3 CHANNEL SELECTION: The ECG text file has two different columns for two leads. A program written in
C/C++ segregates these two signals and using the most significant bit as channel
identifier, two separate channels of analog output were obtained. The two separate
channels are designed by using two LF398 sample and hold ICs connected at the output
of the DAC0808. The most significant bit of the signal decides which channel is being
selected is fed at the eighth pin of the sample and hold IC. The notch filter is designed at
the output of the channel selector which passes signal of specific band i.e. 14-20 Hz.
General description of sample and hold circuit
Figure 4.5 shows the basic connection diagram of sample and hold circuit. It is a
monolithic sample-and-hold circuit, which utilizes BI-FET technology to obtain ultrahigh dc accuracy with fast acquisition of signal and low drop rate. Operating as a unity
gain follower, dc gain accuracy is 0.002% typical and acquisition time is as low as 6 µs
to 0.01%.
A bipolar input stage is used to achieve low offset voltage and wide bandwidth.
Input offset adjust is accomplished with a single pin, and does not degrade input offset
drift. The wide bandwidth allows the LF198 to be included inside the feedback loop of 1
MHz op amps without having stability problems. Input impedance of 1010Ohm allows
high source impedances to be used without degrading accuracy.
Figure 4.5 basic circuit connections of sample and hold circuit
.
Figure 4.6 Pin diagram of Sample and Hold IC
P-channel junction FET's are combined with bipolar devices in the output amplifier to
give droop rates as low as 5 mV/min with a 1 µF hold capacitor. The JFET's have much
lower noise than MOS devices used in previous designs and do not exhibit high
temperature instabilities.
The overall design guarantees no feed-through from input to output in the hold
mode, even for input signals equal to the supply voltages.
Features
•
Less than 10 µs acquisition time
•
TTL, PMOS, CMOS compatible logic input
•
0.5 mV typical hold step at Ch = 0.01 F
•
Low input offset
•
0.002% gain accuracy
•
Low output noise in hold mode
•
Input characteristics do not change during hold mode
•
High supply rejection ratio in sample or hold
•
Wide bandwidth
•
4.5.4
Space qualified, JM38510
QRS DETECTION
The QRS complex is the most striking waveform within the electrocardiogram
(ECG). Since it reflects the electrical activity within the heart during the ventricular
contraction, the time of its occurrence as well as its shape provide much information
about the current state of the heart.
For QRS Detection, a narrow band pass filter has been designed for each channel
by using 741 operational amplifier in inverting mode. The filter is designed to have the
centre frequency 17 Hz and Quality factor of 2.83. It removes all signal frequencies
except for a particular band (i.e. to record 14-20 Hz activity in ECG recordings).
The frequencies occurring on either side of this band are not passed. The red
colored LEDs at the output of filters remains off under normal operating conditions and
flashes a specific number of times indicating which particular channel is selected and
every time the occurrence of QRS complex (highest peak of the ECG signal).
Due to its characteristic shape it serves as the basis for the automated
determination of the heart rate, as an entry point for classification schemes of the cardiac
cycle, and often it is also used in ECG data compression algorithms.
In that sense, QRS detection provides the fundamentals for almost all automated
ECG analysis algorithms. Software QRS detection has been a research topic for more
than 30 years. The evolution of these algorithms clearly reflects the great advances in
computer technology.
Within the last decade many new approaches to QRS detection have been
proposed; for example, algorithms from the field of artificial neural networks, genetic
algorithms, wavelet transforms, filter banks as well as heuristic methods mostly based on
nonlinear transforms.
The QRS complex is a waveform that correlates to the electrical flow through the
bundle branches, from which heart-rate and many other parameters can be measured.
The accurate detection of the R-peak of the QRS complex is the prerequisite for the
reliable function of EKG analyzers .The recognition of almost all EKG parameters is
based on a fixed point identifiable at each cycle. R-peak is suitable for use as the datum
point, because it has the largest amplitude and sharpest waveform that can be extracted
from EKG. The time and amplitude measurements can be performed when the apex of
the R-peak is detected at each cycle.
Figure 4.7 Circuit connection of QRS Detection stage.
One can implement the filtering at the software level using digital filters as well
to remove the noise present in the captured digital EKG. Digital filters are required to be
designed to reduce noise interferences and thereby improve the signal-to-noise ratio.
Filtering EKG signal is not an easy task.
The important EKG signals are found at very low frequencies and are relatively
distributed in the mid frequencies. Typically the important EKG signals are in the range
of 0.5–150Hz.
Chapter 5: ECG Simulator Software
5.1 Introduction
The text file of ECG signal with proper annotation (Markings) was downloaded
from Physionet.org and stored in the folder. The ‘C’ program file named ECG.C was
compiled and its executable file i.e. ECG.EXE was stored in the same folder.
Upon running this executable file, the signal from DAC connected to the parallel
port was displayed on DSO. The flowchart in figure 5.1 shows the step-by-step
procedure of basic program involved in ECG Simulation. A problem that plagues
Windows NT/2000 and Windows XP is its strict control over I/O ports. Unlike Windows
95 & 98, Windows NT/2000/XP will cause an exception (Privileged Instruction) if an
attempt is made to access a port that we are not privileged to talk too. Actually it is not
Windows NT that does this, but any 386 or higher processor running in protected mode.
Direct I/O is the world's first device driver for Microsoft Windows NT, Windows
2000, Windows XP and Windows Server2003 which enables the direct hardware access
for your existing software without any programming efforts on your side. We have
downloaded Direct I/O device driver from site www.direct-io.com.
However for accessing the parallel port correctly, the Direct I/O driver must be in
the same directory than the user mode executable ran and the user must have
administrator privileges. Once the driver has been installed for the first time, any user
with normal user privileges can access the device driver normally. This is ideal in
classroom/corporate environments where security is paramount.
The basic flowchart in figure 5.1 shows the software procedure involved in ECG
simulator. The downloaded ECG data file is opened along with the Direct I/O for
accessing the parallel port of PC. By using the C/C++ programming, the analog
variables of the data file are read and converted into 7- bit digital values. The most
significant bit (MSB) is used for the selection of the dual channel of ECG Simulator.
With the proper time delay calculated by formula Tn - Tn-1, these values are sent to
parallel port of PC until the end of file is reached.
Figure5.1 Flowchart of simulator software
5.2 Parallel Port
PC parallel port can be very useful I/O channel for connecting circuits to PC. PC
parallel port is 25 pin D-shaped female connector in the back of the computer. It is
normally used for connecting computer to printer, but many other types of hardware for
that port is available today.
Not all 25 are needed always. We can easily do with only 8 output pins (data
lines) and signal ground. I have presented those pins in the table below. Those output
pins are adequate for many purposes.
5.2.1 Pin function
2
D0
3
D1
4
D2
5
D3
6
D4
7
D5
8
D6
9
D7
Pins 18,19,20,21,22,23,24 and 25 are all ground pins. Those data pins are TTL
level output pins. This means that they put out ideally 0V when they are in low logic
level (0) and +5V when they are in high logic level (1). In real world the voltages can be
something different from ideal when the circuit is loaded. The output current capacity of
the parallel port is limited to only few mill amperes.
5.2.2 Parallel port programming in DOS
The following examples are short code examples how to write to I/O ports using
different languages. I have used I/O address 378h which is one of the addresses where
parallel port can be. The typical parallel port I/O addresses configurations seen on PCs
with ISA bus:
•
LPT1: 3BCh, LPT2: 378h, LPT3: 278h.
•
LPT1: 378h, LPT2: 278h.
•
LPT1: 378h.
Those are the typical I/O addresses used in ISA bus based systems. In PCI bus
based systems the LPT1 port on motherboard is typically at I/O-address 378h or 3BCh
the following examples are for DOS system (they might or might not work on other
systems). The code examples are designed to be used with LPT1 port that resides in I/O
address 378h.
Assembler
MOV DX, 0378H
MOV AL, n
OUT DX,AL
Where n is the data you want to output.
Basic
OUT &H378, N
Where N is the number you want to output.
C
Outp (0x378, n);
or
Outportb (0x378, n);
Where N is the data that we want to output. The actual I/O port controlling
command varies from compiler to compiler because it is not part of standardized C
libraries. The following port description applies to Standard Parallel Port (SPP).
Offset
Base + 0
Name Read/Write
Data
Port
Write
Bit No.
Properties
Bit 7
Data 7
Bit 6
Data 6
Bit 5
Data 5
Bit 4
Data 4
Bit 3
Data 3
Bit 2
Data 2
Bit 1
Data 1
Bit 0
Data 0
This Data Register is simply used for outputting data on the Parallel Port's data lines
(Pins 2-9). If the port is bi-directional, we can receive data on this address.
Offset
Base + 1
Name Read/Write
Status
Read Only
Port
Bit No.
Properties
Bit 7
Busy
Bit 6
Ack
Bit 5
Paper Out
Bit 4
Select In
Bit 3
Error
Bit 2
IRQ (Not)
Bit 1
Reserved
Bit 0
Reserved
The Status Port (base address + 1) is a read only port. Any data written to this port will
be ignored.
Offset
Name Read/Write
Base + 2 Control Read/Write
Port
Bit No.
Properties
Bit 7
Unused
Bit 6
Unused
Bit 5
Bit 4
Bit 3
Bit 2
Enable BiDirectional Port
Enable IRQ Via
Ack Line
Select Printer
Initialize Printer
(Reset)
Bit 1
Auto Linefeed
Bit 0
Strobe
The Control Port (base address + 2) in intended as a write only port. When a
printer is attached to the Parallel Port, four "controls" are used. These are Strobe, Auto
Linefeed, Initialize and Select Printer, all of which are inverted except Initialize. The
first PC-compatible parallel printer ports were unidirectional, allowing 8-bit data transfer
only from the host to the peripheral. These early Standard Printer Ports (SPP)
implemented eight data lines and used nine handshaking lines, four output from the host
and five input to the host.
The SPP type implemented three registers for the control and monitoring of the
data and handshaking lines; these are the data port, status port, and control port. The SPP
type parallel ports are most commonly used for printers, plotters, keys, etc. Generally all
modern parallel ports can operate in SPP mode. The maximum cable distance between
computer and peripheral could only extend 6 feet.
Later came the PS/2 type bi-directional parallel port (BPP); this bi-directional
port simply added the capability to read 8-bit data from the peripheral to the host. This
parallel port type also implemented the same three registers as used by SPP for the
control and monitoring of the data and handshaking lines; these are the data port, status
port, and control port. In addition to normal operations there is one extra bit on control
port that can set the data pins to output or input mode.
The IEEE 1284 standard, "Standard Signaling Method for a Bi-directional
Parallel Peripheral Interface for Personal Computers", sought to correct the major
drawbacks to the original parallel port structure. IEEE 1284 sets standards for the cable,
connector, and electrical interface, which guarantee interoperability between all parallel
peripherals.
The specified configuration ensures that data integrity is maintained, even at the
highest data rates, and at a distance of up to 30 feet. Two new types of parallel ports with
extended features are now available: the Enhanced Parallel Port (EPP) and the Extended
Capabilities Port (ECP). EPP and ECP are standards defined by IEEE 1284 and
Microsoft ECP Specifications.
Both EPP and ECP ports may be operated in the SPP and bi-directional modes;
however, operation in their feature modes requires both compatible peripherals and
appropriate software drivers. Generally, EPP is used primarily by non-printer
peripherals, CD ROM, tape drive, hard drive, network adapters, etc., while ECP is aimed
at newer generation of printers and scanners. Currently, new products have been released
having support for a mixture of these protocols. With EPP, the software driver may
intermix read and write operations without any overhead or protocol handshaking. With
the ECP protocol, changes in the data direction must be negotiated.
The I/O interface on EPP and ECP ports is somewhat different from normal I/O
port controls. They can be viewed as supersets of SPP. An EPP parallel port implements
two registers in addition to the standard data, status, and control ports. The outputs are
tri-state able outputs allow the EPP port to be used as a data bus for multiple EPP
compatible devices. The entire data transfer occurs within one ISA I/O cycle. An ECP
parallel port features two special modes, namely data and command cycles. The ECP
Parallel Port Mode allows bi-directional data transfer using automatic interlocked
handshaking via the ECP protocol. When the ECP protocol was proposed, a standard
register implementation was also proposed through Microsoft ECP Specification. ECP
protocol is meant to be driven by DMA rather than explicit I/O operations. ECP protocol
is commonly seen on parallel port on motherboards and on high-end parallel port cards
that plug to ISA bus, but often not on PCI bus parallel port cards (because PCI bus does
not support ISA bus type DMA transfers).
Many modern parallel ports support SPPl, BPP, ECP and EPP modes, or at
least most of them. On some systems and interface cards there has been even
options to see USB parallel port adapters
The USB-Parallel Port Adapter enables users to connect parallel port interfaced
devices like printers to a desktop or laptop PC via the PC's USB port. As USB becomes
increasingly popular and newer laptop PCs are without parallel and/or serial ports. Older
PCs tend to have a parallel port but no USB, newer PCs have both, and tomorrow's PCs
will typically have USB but no parallel port.
The parallel port through this kind of adapter looks pretty same as normal
parallel port for high level programs on Windows system. The low level implementation
of them is completely different, and the low level I/O control operations described in this
document do not work with USB parallel port adapters.
At this port we can forget using the USB parallel ports for your own hardware
controlling. In some cases USB Parallel Printer Adapter can be useful. With USB
Parallel Printer Adapter we can attach the printer to our USB port and make room for
your own circuits on the existing legacy parallel ports on our system.
5.3 DIRECT I/O - A Windows NT I/O Port Device Driver
Accessing I/O Ports in protected mode is governed by two events, The I/O
privilege level (IOPL) in the EFLAGS register and the I/O permission bit map of a Task
State Segment (TSS). Under Windows NT, there are only two I/O privilege levels used,
level 0 & level 3. User mode programs will run in privilege level 3, while device drivers
and the kernel will run in privilege level 0, commonly referred to as ring 0. This allows
the trusted operating system and drivers running in kernel mode to access the ports,
while preventing less trusted user mode processes from touching the I/O ports and
causing conflicts. All usermode programs should talk to a device driver which arbitrates
access. The I/O permission bitmap can be used to allow programs not privileged enough
(I.e. usermode programs) the ability to access the I/O ports. When an I/O instruction is
executed, the processors will first check if the task is privileged enough to access the
ports. Should this be the case, the I/O instruction will be executed. However if the task is
not allowed to do I/O, the processor will then check the I/O permission bitmap.
The I/O permission bitmap, as the name suggests uses a single bit to represent
each I/O address. If the bit corresponding to a port is set, then the instruction will
generate an exception however if the bit is clear then the I/O operation will proceed.
This gives a means to allow certain processes to access certain ports. There is one I/O
permission bitmap per task.
5.3.1 Accessing I/O Ports under NT/2000/XP
There are two solutions to solving the problem of I/O access under Windows NT.
The first solution is to write a device driver which runs in ring 0 (I/O privilege level 0) to
access your I/O ports on your behalf. Data can be passed to and from your usermode
program to the device driver via IOCTL calls. The driver can then execute your I/O
instructions. The problem with this is that it assumes we have the source code to make
such a change.
Another possible alternative is to modify the I/O permission bitmap to allow a
particular task, access to certain I/O ports. This grants your usermode program running
in ring 3 to do unrestricted I/O operations on selected ports, per the I/O permission
bitmap. This method is not really recommended, but provides a means of allowing
existing applications to run under windows NT/2000. Writing a device driver to support
your hardware is the preferred method. The device driver should check for any
contentions before accessing the port.
However, using a driver such as Port Talk can become quite inefficient. Each
time an IOCTL call is made to read or writes a byte or word to a port, the processor must
switch from ring 3 to ring 0 perform the operation, then switch back.
5.3.2 Starting and Installing the Direct I/O driver
However for accessing the parallel port correctly, the Direct I/O driver must be in
the same directory than the user mode executable ran and the user must have
administrator privileges. Once the driver has been installed for the first time, any user
with normal user privileges can access the device driver normally. This is ideal in
classroom/corporate environments where security is paramount.
Direct I/O is the world's first device driver for Microsoft Windows NT, Windows
2000, Windows XP and Windows Server2003 which enables the direct hardware access
for your existing software without any programming efforts on your side. We have
downloaded Direct I/O device driver from site www.direct-io.com.
It is especially useful for existing 16bit software which accesses special hardware,
e.g. programmers or data acquisition boards. Even 32bit software developed can have
benefits from the easy access to the hardware.
We never have to bother with complex and expensive DDK toolkits again.
With Direct I/O one can continue to use your existing software and hardware after
migrating to Microsoft Windows NT, Windows 2000, Windows XP and Windows
Server2003. There is no need to update to 32bit versions any more. Here is a brief idea
how easy it is to use Direct I/O. It shows step-by-step how to integrate Direct I/O with
your own application. Let’s imagine we have to write an application named
MYAPP.EXE to control a special hardware with I/O ports in the range 310-31Fh.
1. Enter the resources needed:
2. Give your application the right to access these resources:
Write your application: -
C / C++ ,Visual Basic ,Delphi . Here is an example of C
code.
5.3.3
Features of Direct I/O
Direct I/O is an Application Software with the following features:•
Direct I/ O is a kernel mode driver together with a Virtual Device Driver (VDD).
•
Direct I/ O enables access to I/O ports and memory mapped I/O for both 16bit
and 32bit programs.
•
I/O access is extremely fast. There is no impact on performance caused by Direct
I/O.
•
Interrupt emulation is supported for all 16bit and 32bit programs.
•
Specify the programs which are allowed to use Direct I/ O. The risk of system
corruption is minimal.
•
It is controlled with its own control panel.
•
It comes with a state-of-the-art installer with complete uninstall support.
•
Customization and seamless integration of the installation into your setup can
easily be done by yourself.
•
It is fully compatible with Windows NT, Windows 2000, Windows XP and
Windows Server2003.
•
Direct I/ O includes comprehensive online help.
•
It is shareware. It can be evaluated before buying it.
Chapter 6: Simulated Results and Observations
Simulation is an emerging area of technology. It is completely an interactive
system of medical training based on user of innovative educational tools in highly
realistic context of a clinical scenario. Arterial blood pressure, ECG, Heart frequency,
Spo2, CO2 production and other vital parameters trigger by the simulator are viewed on
monitor. There are different software tools available for simulation and analysis. In this
project ECG data file is executed using a C program and Direct I/O device driver is
installed to make the process easy, fast and accurate.
The advantage of the system offers is that it can mimic in real time responses to
treatment, whether technical or pharmalogical. For clinical training of doctors to
interpret the ECG of a Subject with proved diagnosis (i.e. the exact status of subject’s
heart is known through the clinical truths) we require the Subject, ECG amplifier and
Monitor. The availability of such subject may not be practically feasible in all situations.
The Doctors therefore have to mainly rely on recorded signals which do not give the real
time experience to the Doctors.
An ECG simulator is device which can simulate all types of signals recorded
previously in the real time mode. This simulator can be used both for clinical training of
doctors as well as for design, development and testing of automatic ECG machine
without having real subject for this purpose. The text file of ECG signal with proper
annotation (Markings) was downloaded from http:\physionet.org and stored in the
folder. The ‘C’ program file named ECG.C was compiled and its executable file i.e.
ECG.EXE was stored in the same folder. Upon running this executable file, the signal
from DAC connected to the parallel port was displayed on DSO.
The quality of signal in terms of amplitude, duration and wave shape was similar
to those obtained by signals from human subject & ECG amplifier. In absence of any
Polaroid camera available in the lab, these signals could not be recorded to be
reproduced in this report. However, the peaks annotated in the data file matched with
those detected by peak detector.
Results
The below tables shows the results obtained with the ECG Simulator. The
simulated electric waves were presented to electronic peak detectors The red colored
LEDs at the output of filters remained off under normal operating conditions and flashed
a specific number of times indicating which particular channel is selected and every time
the occurrence of QRS complex (highest peak of the ECG signal). The detected peaks
exactly tallied with the annotated peaks in the given ECG database, thereby
authenticating its efficacy.
Figure 6.1 The peaks detected in ECG signal with leads MLII and V5
Table 6.1 Results for mitdb/100
LEAD
ML II
V5
ML II
V5
ML II
V5
ML II
V5
ML II
V5
ML II
V5
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
Table 6.2 Results for mitdb/102
ANNOTATED
PEAKS
13
13
12
12
12
12
12
12
13
13
12
12
PEAKS
DETECTED
13
13
12
12
12
12
12
12
13
13
12
12
LEAD
V5
V2
V5
V2
V5
V2
V5
V2
V5
V2
V5
V2
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
ANNOTATED
PEAKS
12
12
12
12
12
12
12
12
13
13
12
12
PEAKS
DETECTED
12
12
12
12
12
12
12
12
13
13
12
12
ANNOTATED
PEAKS
11
11
12
12
11
11
12
12
12
12
12
12
PEAKS
DETECTED
11
11
12
12
11
11
12
12
12
12
12
12
ANNOTATED
PEAKS
13
13
12
12
PEAKS
DETECTED
13
13
12
12
Table 6.3 Results for mitdb/103
LEAD
ML II
V2
ML II
V2
ML II
V2
ML II
V2
ML II
V2
ML II
V2
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
Table 6.4 Results for mitdb/104
LEAD
V5
V2
V5
V2
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
V5
V2
V5
V2
V5
V2
V5
V2
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
12
12
13
13
12
12
12
12
12
12
13
13
12
12
12
12
ANNOTATED
PEAKS
14
14
13
13
14
14
14
14
14
14
14
14
PEAKS
DETECTED
14
14
13
13
14
14
14
14
14
14
14
14
ANNOTATED
PEAKS
11
11
PEAKS
DETECTED
11
11
Table 6.5 Results for mitdb/105
LEAD
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
Table 6.6 Results for mitdb/108
LEAD
ML II
V1
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
10
10
10
10
10
10
10
10
9
9
10
10
10
10
10
10
10
10
9
9
ANNOTATED
PEAKS
14
14
15
15
14
14
14
14
14
14
14
14
PEAKS
DETECTED
14
14
15
15
14
14
14
14
14
14
14
14
ANNOTATED
PEAKS
9
PEAKS
DETECTED
9
Table 6.7 Results for mitdb/112
LEAD
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
Table 6.8 Results for mitdb/113
LEAD
ML II
INTERVAL
In seconds
0:00 – 0:10
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
9
10
10
10
10
10
10
9
9
10
10
9
10
10
10
10
10
10
9
9
10
10
ANNOTATED
PEAKS
13
13
13
13
13
13
13
13
13
13
13
13
PEAKS
DETECTED
13
13
13
13
13
13
13
13
13
13
13
13
ANNOTATED
PEAKS
9
9
8
8
8
8
9
9
8
PEAKS
DETECTED
9
9
8
8
8
8
9
9
8
Table 6.9 Results for mitdb/116
LEAD
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
Table 6. 10 Result for mitdb/117
LEAD
ML II
V2
ML II
V2
ML II
V2
ML II
V2
ML II
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
V2
ML II
V2
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
8
8
8
8
8
8
ANNOTATED
PEAKS
10
10
10
10
10
10
10
10
10
10
10
10
PEAKS
DETECTED
10
10
10
10
10
10
10
10
10
10
10
10
ANNOTATED
PEAKS
15
15
15
15
15
15
14
14
14
14
14
14
PEAKS
DETECTED
15
15
15
15
15
15
14
14
14
14
14
14
Table 6.11 Result for mitdb/121
LEAD
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
Table 6.12 Result for mitdb/122
LEAD
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
ML II
V1
INTERVAL
In seconds
0:00 – 0:10
0:00 – 0:10
0:10 – 0:20
0:10 – 0:20
0:20 – 0:30
0:20 – 0:30
0:30 – 0:40
0:30 – 0:40
0:40 – 0:50
0:40 – 0:50
0:50 – 0:60
0:50 – 0:60
Chapter 7: Conclusions and Future Scope
The project was successfully implemented to simulate Dual channel ECG signal
in terms of signal amplitude, duration and waveform. The simulated electric waves were
presented to electronic peak detectors. The detected peaks exactly tallied with the
annotated peaks in the given ECG database, thereby authenticating its efficacy.
Since, all the output lines of the parallel port were not fully exploited in this
endeavourer an attempt should be made to develop multichannel ECG simulator.
References
[1]
Moody, G.B. (1992) “ECG Database Application Guide” Harvard Univ.
MIT- Div. Health Science &Technology, Cambridge –MA.
[2]
www.gouldis.com/product 429/12-lead ECG amplifier
[3]
PhysioBank Archive Index, Resource for ECG Databases:
http://www.physionet.org/physiobank/database.
[4]
Moody, G.B, Mark, R.G (1990) “The MIT- BIH Arrhythmia Database on
CD- ROM & Software for use with it.” Computers in Cardiology,
Proceedings, pp 185-188.
[5]
Goldberger, A.L, Amaral, L.A.N, Glass, L.,Haudorff, J.M, Ivanov, P.Ch,
Mark, R.G, Mietus, J.E, Moody, G.B, Peng, C.K, Stanley, H.E.(2000)
“Physiobank, Physiotoolkit, &PhysioNet: Components of a New Research
Resource for Complex Physiologic Signals” circulation 101(23):e.215-e220[
Circulation electronics pages; http://circ.ahajournals.org/cgi/contents
/full/101/23/e215.
[6]
W.G. John, (1998) “Medical Instrumentation: Application and Design”
Edition. 3rd, Toronto: Johan Wiley and sons
[7]
www.perfusion.com.au/ccp/biomedical%20 electronics/biomed/ECG%20
amplifier.htm
[8]
Cromwell L, Weibe F. J., “Biomedical Instrumentation and Measurements”
[9]
Hobbie R. K, (1973) “The Electrocardiogram as an Example of
Electrostatics” Am. J. Phys. 42, 824
[10]
Ifeachor E.C. and .Jervis B.W (2002)., “Digital Signal Processing, A
Practical Approach”, Prentice Hall,
Publication from this Research Work
[1]
Mandeep Singh, Gurpinder kaur “Design of Single Channel ECG Simulator”,
National Conference on Advancement in Modeling & Simulation Jan-20-21
AIMS2006, pp.10-13, LLRIET, Moga, Punjab, India.